6.1. Cleaning the fuel pre-filter element
1. Open the fuel tank filler cap and relieve the pressure in the fuel tank.
2. Remove any dirt from the outside of the fuel pre-filter.
3. Unscrew cover 1 and remove pre-filter housing 4 together with filter element 3 (figure 1.11). Replace the filter element if it is damaged or heavily clogged.
4. Wipe cover 1 and filter element 3.
5. Check the O-ring 2. Apply sealant or install a new O-ring.
6. Install cover 1 together with filter element 3 and tighten it.
7. Check for fuel leaks.
Figure 1.11. Cleaning the fuel pre-filter element: 1 - Lid; 2 - Sealing ring; 3 - Filter element; 4 - Pre-filter housing.
6.2. Replacing the fuel filter
Engines 602.984/985
1. Unscrew bolt 2 and remove filter element 1 (figure 1.12).
2. Replace the sealing ring 3.
3. Install the new filter element and tighten the bolt to 16 Nm.
4. Start the engine and let it run at 1500 rpm for one minute to bleed the filter.
5. Check for fuel leaks.
Figure 1.12. Replacing the fuel filter on engines 602.984/98: 1 - Filter; 2 - Bolt; 3 - Sealing ring.
[Original source of information: MercedesMAN.ru]
Engines 904
6. Unscrew cover 1 and slowly lower filter housing 5 together with filter element 2 (figure 1.13 a, b).
7. Remove the cover together with the filter element and unhook the filter element by pressing on it from the side.
8. Remove dirt trap 3 from the filter housing.
9. Wipe the lid and dirt trap.
10. Replace the rubber sealing ring 4.
11. Install all removed components in the reverse order of removal.
12. Check for fuel leaks.
Figure 1.13a. Unscrew cover 1 of the fuel filter.
Figure 1.136. Disassembled fuel filter.